Floating point exception on a int Array - C

Question

int check_row;
    for (n=0; n<9; n++) {
 used_numbers[n] = n+1;
}
for (row=0; row<3; row++) {
    for (check_row=0; check_row<3; check_row++) {
        used_numbers[(sudoku[row][check_row]-1)] = 0;
    }
...

int sudoku[9][9] declared as global variable and used_numbers[9] as int. In sudoku matrix for row from 0 to 2 and col from 0 to 2 for each row, has in it, numbers > 0

At this point I get "Floating point exception", how resolve this? sorry for my bad english...

Answer 1

It is a very bad idea to have function/variable definitions in a header file, like you have done. Put the definitions in a C file, and the declarations in a header file for other C files to use.

Your floating-point error is on line 66 of sudoku.h, not where you think it is.

number = rand()%m;

Since m is zero here, dividing by it results in the error.

I haven't looked at the whole code in detail.

Answer 2

@Alok has of course told you what the error is (and pointed out problems with your .h file), but I want to show you how you can find it yourself.

1. First, you want to build with debugging. I ran: gcc -g sudoku.c -o sudoku
2. Second, I ran it and confirmed it does indeed crash with Floating point exception.
3. I ran gdb sudoku to start the debugger.
4. I typed 'run', and shortly thereafter:

GDB output:

(gdb) run
Starting program: /tmp/t/sudoku 

Program received signal SIGFPE, Arithmetic exception.
0x000000000040098f in sudoku_init () at sudoku.h:66
66                              number = rand()%m;

So, we have the line number it's at. Using l more context can be printed. Using p m we can see that m==0, which would indeed be a problem.